Statistical analysis of measured underwater radiated noise from merchant ships using ship operational and design parameters.

Ships unintentionally radiate underwater noise mainly due to propeller cavitation under usual operations. In 2022, the International Maritime Organization started a review of the nonmandatory guidelines for the reduction of underwater radiated noise (URN) from ships. The characteristics of URN from ships have been studied for a long time, and quantitative variations in URN levels with ship size and speed have been reported. From the viewpoint of ship design, it is more reasonable that the effect of ship speed and draft is considered as the ratio to design speed and maximum draft, respectively. Therefore, in this study, underwater sound measurements were conducted in deep water (>300 m in depth) under a sea lane, and regression analysis was applied to the source levels of the URN from many merchant ships using ship length, ship speed ratio to design speed, and draft ratio to maximum draft. In this analysis, the source level is simplified based on the characteristics of URN due to propeller cavitation. This allows one coefficient to represent the approximate shape of the spectrum of URN level. Further, variations in the URN level for each ship type are discussed based on the results and comparisons with previous studies.

Change in singing behavior of humpback whales caused by shipping noise.

Reactions of singing behavior of individual humpback whales (Megaptera novaeangliae) to a specific shipping noise were examined. Two autonomous recorders separated by 3.0 km were used for the acoustic monitoring of each individual song sequence. A passenger-cargo liner was operated once per day, and other large ship noise was excluded given the remote location of the Ogasawara Islands, 1000 km south of Tokyo. In total, locations of between 26 and 27 singers were measured acoustically using time arrival difference at both stereo recorders on the ship presence and absence days, respectively. Source level of the ship (157 dB rms re 1µPa) was measured separately in deep water. Fewer whales sang nearby, within 500 m, of the shipping lane. Humpback whales reduced sound production after the ship passed, when the minimum distance to the whale from the ship trajectory was 1200 m. In the Ogasawara water, humpback whales seemed to stop singing temporarily rather than modifying sound characteristics of their song such as through frequency shifting or source level elevation. This could be a cost effective adaptation because the propagation loss at 500 m from the sound source is as high as 54 dB. The focal ship was 500 m away within several minutes. Responses may differ where ship traffic is heavy, because avoiding an approaching ship may be difficult when many sound sources exist.

Are acetabular component alignment guides for total hip arthroplasty accurate?

The acetabular component orientation of total hip arthroplasty is of critical importance to the clinical results. Although navigation systems have recently been introduced, acetabular component alignment guides are still used in most of ordinary hospitals. However, the accuracy of alignment guides themselves has not been evaluated. Fifteen types of alignment guide were examined. In all the alignment guides, the angles actually indicated and those stated by manufacturers were different. Our results showed that usage of modern alignment guides inherently misleads anteversion into decrease by a mean of 6 degrees (maximum, 12 degrees ) and inclination into increase by a mean of 2 degrees (maximum: 4 degrees ). Such setting of alignment guides could be one of the factors of error in acetabular component orientation.

Comparison between highly cross-linked and conventional polyethylene in total knee arthroplasty.

The use of highly cross-linked polyethylene in total knee prostheses is still controversial. The aim of the present study was to compare radiographic and clinical results of using conventional and highly cross-linked polyethylene in cruciate retaining total knee prostheses of completely the same design. Two hundred and two consecutive total knee arthroplasties (NexGen CR, Zimmer) were performed using the same procedure. The first consecutive 113 knees had conventional polyethylene insert and following consecutive 89 knees had highly cross-linked polyethylene insert (Prolong, Zimmer). Differences in the age, gender, and diagnosis between two groups were not statistically significant. Preoperative range of motion (ROM) of the knee, and Knee Society Score (KSS) was better in highly cross-linked polyethylene group. Clinical and radiographic results were evaluated at two years after operation. The difference of ROM and KSS between groups was not statistically significant. There was no revision surgery. No knee exhibited osteolysis, aseptic loosening, or polyethylene failure. There was no early catastrophic clinical failure due to use of the new material.

Progression of osteoarthritis of the knee after unilateral total hip arthroplasty: minimum 10-year follow-up study.

INTRODUCTION: Patients undergoing total hip arthroplasty (THA) exhibit changes in the alignment of lower extremities following the procedure, and these changes may exert effects on other joints over the long-term. Therefore, we investigated the course of knee osteoarthritis in patients undergoing long-term follow up after THA, in addition to the relationship between the course of knee osteoarthritis and alignment of lower extremities. MATERIALS AND METHODS: We retrospectively performed radiographic evaluation of the course of knee osteoarthritis (OA) after THA. Thirty patients undergoing successful unilateral THA were followed for a minimum of 10 years. RESULTS: Eleven (33%) subjects showed progression of medial tibiofemoral OA on the non-THA side, while only three (10%) showed progression on the THA side, and this difference was significant (P = 0.033). In addition, the mechanical axes on the THA side passed through more lateral regions of the tibial plateau than those on the non-THA side (P = 0.044). CONCLUSION: Medial tibiofemoral OA on the THA side was less likely to deteriorate than on the non-THA side. The reduced vulnerability to OA progression on the THA side may be due to the lower offset and resultant lateral shift in mechanical axes.

Kinematic comparison between mobile-bearing and fixed-bearing inserts in NexGen legacy posterior stabilized flex total knee arthroplasty.

Femoral component rollback and tibial rotation were evaluated using lateral radiographs taken during passive knee flexion under fluoroscopy in NexGen Legacy Posterior Stabilized Flex (Zimmer, Warsaw, Ind) total knee arthroplasties (TKAs; 30 with mobile insert and 26 with fixed insert). Measured maximal flexion angle demonstrated no significant differences. Femoral component rollback was observed predominantly in TKAs with fixed insert in more than 45 degrees flexion and correlated with maximal flexion angle in each group. Tibial internal rotation was more significant in TKAs with mobile insert in maximal flexion. However, tibial internal rotation from 90 degrees to maximal flexion, which demonstrated correlation with maximal flexion angle in each group, did not show significant difference. The kinematic differences between 2 inserts seemed to have little relevance to the maximal flexion angle.

Correlation between femoral neck version and strain on the femur after insertion of femoral prosthesis.

Stress analysis on the femur after insertion of a femoral prosthesis with a modular interchangeable neck with adjustable neck version was performed using in vitro experimental procedures and cemented strain gauges. Although strain on the anterior and posterior aspects was less than on the medial and lateral aspects, it was more markedly affected by adjusting the interchangeable neck from straight to anteverted (or retroverted) than strain on the medial and lateral aspects, particularly around the stem tip. There was a highly significant correlation between compressive strain on the side toward which the prosthetic neck was oriented and the extent of neck version, whether anteverted or retroverted. Insertion of a femoral implant in excessive anteversion (or retroversion) may cause noticeably increased stress on the anterior and posterior aspects of the proximal femoral shaft.

[Heterotopic ossification in spinal cord injured patients].

Heterotopic ossification after spinal cord injury, most commonly affecting the hip, can represent a significant problem in function and mobility of the patient. Attempt of reduction by medication is unsatisfactory once it developed. In addition, surgical removal is often associated with infection and recurrence. Disodium etidronate is an agent effecting on prevention of development and prophylaxis of ossification.